(1) Field of the Invention
The invention relates to the use of an anisotropic conductive film, having conductive particles in an insulating adhesive, with tape automated bonding to form interconnections between a lead array and an integrated circuit element. The use of an anisotropic conductive film provides a bonding process with reduced temperature and pressure and a reliable encapsulated bonded structure.
(2) Description of Related Art
In conventional tape automated bonding high temperatures are required to form the bond between the inner lead ends of a lead array and the bonding pads on an integrated circuit element. The difference in thermal expansion between the elements of the assembly can distort the lead array and make subsequent processing, such as bonding the outer lead ends, difficult. This invention provides a method to avoid this problem by using an anisotropic conductive film in combination with tape automated bonding. The anisotropic conductive film comprises conductive particles in an insulating adhesive.
U.S. Pat. No. 4,963,002 to Tagusa et al. describes a connection construction using conductive particles and both conductive and insulating adhesives. Japanese Patent 3-62927 to Fujimoto describes a composite conductive particle, an adhesive layer, and flip chip bonding.
U.S. Pat. No. 5,001,542 to Tsukagoshi et al. describes a board made of glass, synthetic resin, metal ceramic or their composite materials. One variation of the disclosed board has a center part removed for a film carrier or TAB structure. Tsukagoshi et al. use a combination of deformable conducting particles, rigid conducting particles, and an adhesive to form the electrical bond. The Tape Automated bonding structure and method of this Invention uses a different, and more flexible, lead frame. This Invention uses an anisotropic conducting film using an adhesive with a different type conducting particles than Tsukagoshi et al. The method used to form the bond are different from Tsukagoshi et al.
U.S. Pat. No. 4,470,657 to Tsukagoshi et al. describes the use of an anisotropic conductive film using an adhesive with conductive particles of multiple sizes. Tape Automated Bonding is not described in this patent.
U.S. Pat. No. 4,731,282 to Tsukagoshi et al. describes insulating adhesives.